1. Field of the Invention
The present invention relates to an electrically conductive metal tape for manufacturing electrical contact components as well as a plug connector made of it.
2. Description of Related Art
Plug contact connectors are widespread in electronic applications. Basically, a mechanical device is understood by this, made up of a plug and plug socket for opening and closing an electrically conductive connection. Plug contact connections are used in the most varied application areas, for example in motor vehicle electrical equipment, news technology or industrial plant electronics.
A common manufacturing method of such plug contact elements is to punch out blanks from a copper or copper alloy tape, and to process these further into plug contact elements. Copper has high conductivity. To protect against corrosion and wear, as well as to raise surface hardness, the copper or copper alloy tapes are first tinned. Tin is suitable because of its good corrosion stability, especially as coating material for copper. Applying the layer by the hot-dip method counts as a part of standard technology.
In this connection, the most varied tin alloys are known for surface coating the base material, particularly including tin-silver alloys, since these count among the very good contact materials.
As described in European Patent No. 0 443 291, the base material of one plug contact element in an electrical plug connector pair is coated with pure tin or a tin-lead alloy, while the other plug contact element has a harder surface coating, applied in a molten procedure, of an alloy containing up to 10% by weight of silver. Besides silver, several further alloying metals are suggested. This approach points the way on manufacturing high quality plug connectors having constant, low contact resistance and least possible force (required) for plugging and unplugging.
The proposal according to German Patent No. 44 43 461 provides a surface coating of a tin alloy, applied molten, having up to 5% by weight of cobalt. Besides cobalt, the tin alloy can also contain bismuth and indium, as well as a plurality of additional alloying elements.
German Patent No. 36 28 783 describes an electrical connecting piece made of a copper alloy which has 0.3 to 2% by weight of magnesium, as well as 0.001 to 0.1% by weight of phosphorus. The electrical connecting pieces are distinguished by their strength, their electrical conductivity and strain relaxation properties at raised temperatures. They display satisfactory properties in use, even when produced in compact sizes and complicated shapes.
From German laid-open document No. 43 38 769, a copper alloy is also among the related art, for producing electrical plug connectors with a composition of essentially 0.5 to 3% by weight of nickel, 0.1 to 0.9% by weight of tin, 0.08 to 0.8% by weight of silicon, 0.1 to 0.3% by weight of zinc, 0.007 to 0.25% by weight of iron, 0.001 to 0.2% by weight of phosphorus, as well as 0.001 to 0.2% magnesium, having the principal component copper including as remainders the unavoidable impurities.
The known metal tapes, or rather, the plug connectors made of them have proven themselves in practice. However, the technical and qualitative requirements on contact components are growing increasingly, with regard to their mechanical and electrical properties. That is true particularly when the contact components are used under difficult or aggressive environmental conditions, e.g. for plug connectors in motor vehicle electrical equipment, and there, above all, in the electronics of the engine. Under such difficult application conditions, requirements can come up, particularly with regard to temperature stability, relaxation stability, corrosion resistance and adhesive strength of the coating, in which the known contact components are pushed to their limit. Peeling of the surface coating can then occur.
It is an object of the invention to create an electrically conductive metal tape for manufacturing electrical contact components, in particular plug connectors, with good electrical and mechanical properties, while improving the adhesion between base material and coating, which is of additional economic advantage.
This and other objects of the invention are attained by an electrically conductive metal tape for manufacturing electrical contact components, in particular plug connectors, having a base material made of a copper alloy which has a metal coating, applied using melting technology, made of tin-silver alloy, with an intermetallic phase being formed between the base material and the coating, wherein the base material includes, expressed in percentage by weight:
the remainder being copper and including impurities resulting from smelting. The coating includes a tin-silver alloy having a silver proportion between 1% by weight and 3.8% by weight. In a preferred embodiment, the invention is a plug connector made from the electrically conductive metal tape.